ADLINK Technology USB-1901, User Manual

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Calibration 65
USB-1900 Series
5 Calibration
This chapter introduces the calibration process to optimize AD
conversion and avoid DA output errors.
5.1 Loading Calibration Constants
The USB-1900 Series is factory-calibrated before shipment. The
associated calibration constants of the TrimDACs firmware are
written to the onboard EEPROM. TrimDACs firmware is the algo-
rithm in the FPGA. Loading calibration constants entails loading
the values of TrimDACs firmware stored in the onboard EEPROM.
ADKLINK provides a software utility that automatically reads the
calibration constants, if necessary.
Dedicated space for storing calibration constants is provided in the
EEPROM. In addition to the default bank of factory calibration con-
stants, there is one user-utilization bank, allowing loading of the
TrimDACs firmware values either from the original factory calibra-
tion or a subsequently-performed calibration.
Since measurement and output errors may vary depending on
time and temperature, it is recommended that you calibrate the
USB-1900 Series module in your existing testing environment, as
follows.
5.2 Auto-Calibration (USB-1901/1902 only)
USB-1902 auto-calibration utility measures and corrects almost all
calibration errors with no external signal connections, reference
voltage, or measurement devices. The USB-1900 Series provides
onboard calibration reference to ensure the accuracy of auto-cali-
bration. The reference voltage is measured in the production line
by a digital potentiometer and compensated in the software. The
calibration constant is stored after this measurement.